The present invention refers to an equipment assembly meant to promote the hanging, locking and sealing of a submarine oil-well tubing.
It is the scope of the present invention to provide a set of pieces of equipment for the support, locking and sealing of the tubing of a submarine oil-well, the two last functions being performed by a double hydraulic packer (for production), besides establishing a method for the use of the referred set.
To make the oil produced by an oil-well flow it is necessary to perform several operations from the beginning of the drilling until its effective production. Several pipings are installed in the well, by operations the experts call pipe running (in-hole running).
These pipes carry out the lining of the well, in this case called "casing", or serve to lead the oil to the set of equipments existing on the sea bed, where the wellhead and the Christmas-tree are located.
Simply speaking, the purpose of the wellhead is to support the load of the several hangers where the well casing and the production tubing are fixed on and also provides means of sealing the well to prevent leaks, and also as a support for the set of valves, seals and control devices that enable the connection of the well with the piping which takes the oil to the storage- or processing place. This last set is called Christmas-tree by the specialists. In the case of submarine producing oil-wells the experts denominate these sets as "Submarine wellhead" and "Wet Christmas-tree".
The operations of preparing an oil-well for production are called "completion" by the technical people. Among the completion operations one is highlighted for presenting a large amount of failures, causing large losses to the operations, which is the placing of the tubing hanger. The tubing hanger basically has the functions of supporting the tubing, to lock the tubing against axial movements and, finally, to provide the sealing at the casing hanger where it is sustained.
The large amount of failures on the tubing hangers is due to their locking and their sealing being performed by elements with relatively small dimensions as compared to the size of the referred tubing hanger which makes this latter easily subjected to damages. This is worsened by the fact that very often debris from the sea bed settle on the surface of the casing hanger, where the tubing hanger will be supported in order to be locked and sealed, making the success of these operations more difficult. The settlement of debris is unavoidable because it results from the turbulence caused by placing the pieces of equipment on the wellhead, which stirs the debris in the vicinity of the well.
Another factor to be taken into consideration is the complexity of the tubing hanger hydraulic running tool, which needs for its operation the use of a complex piece of equipment the specialists call "completion riser". The hydraulic running tool will need up to four hydraulic functions to place the tubing hanger, which means a piece of equipment of difficult maintenance due to its high number of components.
The above-mentioned problems cause large loss of time and, as a consequence, rising of costs due to the high number of steps needed to perform the operation of placing the tubing hanger, not mentioning the cost of unforeseen extra operations to correct failures that may occur.
It is clearly seen that the current art, besides not providing the needed safety for the tubing hanger placing operation, frequently leads to an increase in the final costs of the operations due to the necessity of not scheduled operations for correction of problems.